Gas-filled separable contacts for high-voltage switchgear

ABSTRACT

A chamber filled with high-pressure SF6 surrounds the disconnect contacts of a circuit breaker when the breaker is connected to the cooperating terminals of a metal-clad switchgear housing to permit a relatively short bushing length.

United States Patent Inventor Otto Jensen Plymouth, British W. indiesAppl. No. 75,113 Filed Sept. 24, 1970 Patented Nov. 16, 1971 Assigneel-T-E Imperial Corporation Philadelphia, Pa.

GAS-FILLED SEPARABLE CONTACTS FOR HIGH- VOLTAGE SWITCHGEAR 6 Claims, 5Drawing Figs.

U.S. Cl 200/148 R, 200/50 AA int. Cl H0lh 33/54 [50] Field of Search200/ l 48, 50 AA, M80. 148 B References Cited UNITED STATES PATENTS3,278,712 10/1966 Tominaga .i Primary Examiner-Robert S. Macon ZOO/148A!!orney0strolenk, Faber, Gerb & Soffen ABSTRACT: A chamber filled withhigh-pressure SF, surrounds the disconnect contacts of a circuit breakerwhen the breaker is connected to the cooperating terminals ofa metalcladswitchgear housing to permit a relatively short bushing length.

GAS-FILLED SEPARABLE CONTACTS FOR HIGH- VOLTAGE SWITCIIGEAR BACKGROUNDOF THE INVENTION This invention relates to a disconnect contactconstruction for metal-clad switchgear, and more particularly relates toa novel disconnect contact structure which may be filled with ahigh-dielectric gas so that the distance from grounded structures tolive conducting members can be relatively short.

The present invention permits the practical extension of metal-cladswitchgear concepts to voltage classes up to and in excess of 34 kv.Thus, a such voltages, it is useful to use dielectric gas insulatedswitchgear and circuit breakers. However, the contact bushings for thebreaker element becomes excessively long since, when the breaker isconnected, a long path is needed through air from the contact to thegrounded metallic housing.

In accordance with the present invention, the exposed conductor of thecircuit breaker is enclosed in an atmosphere of pressurized dielectricgas when the breaker disconnect contacts move toward engagement withtheir cooperating stationary contacts in the switchgear cubicle. Thus,the bushing length can be appreciably shorter than if the atmospherewere air. Moreover, the gas volume surrounding the disconnect contactsis relatively small so that very little gas is lost when the disconnectcontacts are opened.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is an elevation view of themetal enclosure with the disconnect contact shutter closed.

FIG. 2 is a side cross-sectional view of FIG. 1 with the circuit breakerin its disconnected position.

FIG. 3 is a longitudinal cross-sectional view of one of the pairs ofdisconnect contacts of FIGS. 1 and 2 just after the circuit breakercontact has entered the stationary bushing of the metal enclosure.

FIG. 4 is similar to FIG. 3 and shows the movable disconnect contact inits fully extended but disengaged position.

FIG. 5 is a similar to FIG. 4 and shows the disconnect contacts in theirengaged position.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring first toFIGS. 1 and 2, there is illustrated a conventional metal enclosure whichreceives a plurality of bus bars schematically shown in FIGS. 1 and 2 asbus bars 11 to 16. Bus bars 11-12, 13-14 and 15-16 are conductors ofthree respective phases, and are housed and supported within suitableinsulation bushings 17 to 22, respectively, for conductors 11 to 16.Each of the bushings such as bushing 19 extend through a wall 30 inhousing 10, as shown in FIG. 2, and their open ends are covered by asliding shutter 31 which has suitable shutter openings 33 to 37. Whenthe shutter is moved upwardly, circuit breaker terminals can beconnected to the bus conductors 11 to 16. When, however, such circuitbreakers are racked to a disconnected position relative to buses 11 to16, the grounded shutter 31 is closed to prevent accidental contact withany live conductor elements.

In accordance with the invention, the concept of metal-enclosedswitchgear is extended to higher voltage classes, for example, 34 kv.and up, whereby the bus conductors 11 to 16 are elements of agas-insulated transmission bus system of a type well known to the art.Moreover, and further in accordance with the invention, the circuitinterrupters are also of the high-dielectric gas type, shown, forexample, in copending application Ser. No. 823,1 l5 (C-l354[ER]), filedMay 8, I969 in the name of Otto Jensen, entitled GAS BLAST CIR- CUITINTERRUPTER USING MAIN MOVABLE CON- TACT AS BLAST VALVE, and assigned tothe assignee of the present invention. Thus, in FIG. 2, such a circuitinterrupter is shown as the interrupter 40 which is a truck-mounted unithaving three poles, only the center pole 41 being shown.

Center pole 41 consists of a tank 42, which is suitably supported in atruck frame 43 which can be racked or otherwise moved toward and awayfrom the shutter 31 and bushings 19 and 20. The pole 41 then hasterminal bushings 44 and 45, which will be described more fullyhereinafter, which are suitably sized to pass through the shutteropenings 34 and 45 when the shutter is open to engage the correspondingbushings 19 and 20. When the circuit breaker is moved to its connectedposition, the circuit breaker contacts, schematically illustrated ascontacts 46, will be connected to and in series with conductors l3 and14. Clearly, two similar circuit breaker poles will be provided forconductors 11 and 12 and for conductors I5 and 16, respectively.

In accordance with the invention, the bushings 44 and 45 and thecooperating bushings and disconnect contact structures at the ends ofeach of buses 11 to 16 are so arranged that the contacts are surroundedby high-dielectric gas when the contacts are closed, whereby liveconductive components are permanently surrounded by high-dielectric gas,to permit relatively short bushing lengths for the circuit breakerbushings 44 and 45 and for the cooperating bus bushings extending beyondwall 30 of FIG. 2. This bushing and contact structure is typically shownfor contact 44 in FIGS. 3, 4, and 5 which show the disconnect contactsin various positions.

Components of FIGS. 3, 4 and 5 which are similar to those of FIGS. 1 and2 have been given similar identifying numerals. Thus, FIGS. 3, 4 and 5illustrate the bushing 19 as being supported on wall member 30 by asuitable flange 60 which may be bolted (not shown) to wall member 30.Bushing 19, which may be of a suitable insulation epoxy material, isfurther provided with an inwardly extending web section, such as web 61,which secures conductor 13 in position. The interior of bushing 19 isfilled with sulfur hexafluoride under a pressure of, for example, 4atmospheres. Bushing 19 is then provided with an interior wall 62, whichhas a central opening therein, which slidably receives a conductiveplunger contact 63.

Contact 63 contains a flange stop 64 and receives a gastight gasketfitting 65 which is so constructed that plunger 63 may slide axiallywhile maintaining a gastight fitting within the wall 62, thereby forminga permanent seal to sulfur hexafluoride within cavity 66. The end ofcontact 13 is then provided with a tulip clip" type contact 67 fixedthereon and consisting of the usual contact fingers which are pressedinwardly by suitable biasing springs, such as the springs 68 and 69.Note that the upper end of contact 67 is permanently fixed to the end ofconductor 13 and serves as the stationary disconnect contact of thesystem. Clearly, other similar types of disconnect arrangements could beused for providing a disconnectable contact between the upper end ofplunger 63 and the end of conductor 13.

The interior surface of bushing 19 is then provided with an internalsliding ring seal 70, which will be seen later to form a gastightsliding connection to the surface of bushing 44 when the circuit breakeris moved to a connected position relative to the bus bars within housing10. The bushing 44, as described previously, extends from the tank wall42 of the circuit breaker and is connected to wall 42 by a suitableflange 71. Bushing 44 consists of a conductive cylinder 72 covered withan insulation sheath 73, with the end of conductor 72 being encircled bya plurality of sliding contact fingers which includes contact fingers 74and 75 which are permanently secured to the upper end of conductor 72and are pressed inwardly by suitable biasing springs extending aroundtheir lateral exterior surfaces. These contacts serve to make slidingcontact over the exterior surface of plunger 63, as will be describedmore fully hereinafter.

The interior of conductor 72 then receive a sliding piston whichcontains a central relief valve 81 which is biased to a sealed positionby compression spring 82. The valve 81 has an extension 83 at its uppersurface which can engage the bottom of plunger 63 in order to open thevalve 81. A biasing spring 84 is then applied between piston 80 andshoulder 85 to bias piston 80 upwardly.

As is shown schematically in FIG. 3 and since the circuit breaker 40 isof the two-pressure type, as described in copending application Ser. No.823,115 (C1354[ER]), sulfur hexafluoride at two pressures will beavailable and can be appropriately connected to the interior ofconductor 72. Thus, a first pressure source 90 can be connected to theinterior of conductor 72 by operation of its control valve 91 wherepressure source 90 could, for example, be at a pressure of about 3atmospheres. Alternatively, pressure source 92, which is controlled byvalve 93, may be connected to the interior of conductor 72 where thepressure source 92 might be of a pressure of i5 atmospheres.

The operation of the system is as follows:

FIG. 3 shows the location of the components after the grounded metallicshutter 31, which normally blocks the entrance of each terminal entranceport, has been opened and the breaker terminal assembly carrying theflexible contacts 74 and 75 has partly entered the switchboard bushing19 and contact fingers 74 and 75 are in sliding engagementwith plunger63. The plunger 63 is held in the position shown in H0. 3 by thepressure in chamber 66 which is sufficiently high to overcome thefrictional force on plunger 63 which would tend to move it upwardly. Atthis time, it will also be noted that the pressure in the interior ofconductor 72 is taken from source 90 and will be a lower pressure thanthe pressure within chamber 66.

As the circuit breaker continues to move toward its connected position,and as shown in FIG. 4, the top of plunger 83 carried in piston 80engages the bottom of plunger 63 and the valve 81 is opened against theforce of spring 82. Note that the sliding fingers 74 and 75 of thecontact cluster on the end of conductor 72 continue to move upwardlyover the surface of plunger 63. The opening of valve 81 permits the flowof relatively low-pressure gas (3 atmospheres) from the interior ofconductor 72 through valve 81, through the center of piston 80 and intothe volume surrounding lunger 63 and the contacts, such as contacts 74and 75, at the end of conductor 72. This gas will then dilute andreplace the air previously in this confined space. The continuedpenetration of the breaker bushing 44 then brings the outer surface ofinsulation sleeve 73 into sealing engagement with the O-ring seal 70 sothat the gas surrounding the metallic components including the end ofconductor 72, contacts 74 and 75 and plunger 63 are immersed in ahigh-dielectric gas. Once the position of FIG. 4 is reached, the circuitbreaker is physically in its final position and the disconnect contactscan now safely be closed since all conductive elements are encased in ahigh-dielectric gas so that the distance between these conductivemembers and the grounded shutter 31 can be relatively small. Thus, theoperator of the circuit breaker can operate valves 91 and 93 (FIG. 3)such that valve 91 is closed and valve 93 opened to apply the higherpressure of source 92 to the interior of conductor 72 and beneath piston80. Piston 80, under the relatively high pressure of source 92, is thenmoved upwardly from the position of P10. 4 to the position of FIG. 5driving the plunger 63 before it so that plunger 63 engages tulip clipcontact 67, thereby closing the disconnect contacts. Note that duringthis time, the circuit breaker contacts preferably are open so that thedisconnect contacts do not close an energized circuit.

As pointed out previously, since the plunger 63 and contacts 74 and 75are now enclosed in a high-pressure dielectric gas, the length of thebushing portion 19 between the disconnect finger assembly includingfingers 74 and 75 and the grounded shutter 31 may be very short. Thus, aconductive switchboard container and grounded metallic shutter can beused to cover the switchboard entrance bushing without fear of flashovereven though the potential of conductor 13 to ground may be 34 kv. orhigher. Moreover, the high-pressure gas in the bushing assemblies willpermit substantial reductions in size for the various bushings. Finally,it will be clear that special gas systems will not be necessary sincethe novel invention incorporates the gas pressure and gas medium whichare normally used by the circuit breaker.

in order to open the disconnect contacts of FIGS. 3, 4 and 5, thecircuit breaker poles are first operated. Thereafter,

valve 93 is closed and valve 91 opened such that the pressure beneathpiston decreases to the lower pressure of source 90. This then causesthe plunger 63 to be moved downwardly from the position of FIG. 5 to theposition of F IG. 4, thereby to open the disconnect contacts. The valve91 may then be closed and the breaker is then racked from the positionof FIG. 4 to the position of FIG. 3 in order to open the disconnectcontacts by causing sliding contacts 74 and 75 to slide off of the endof plunger 63. Note that the only gas which is lost during the openingoperation is the small volume of gas which has been trapped beneath wall62 in FIGS. 3, 4 and 5 and above the ring-shaped seal 70, with this gasbeing exhausted to the external atmosphere when the outer surface ofbushing 44 clears ring 70.

Although this invention has been described with respect to preferredembodiments, it should be understood that many variations andmodifications will now be obvious to those skilled in the art and,therefore, the scope of this invention is limited not by the specificdisclosure herein, but only by the appended claims.

The embodiments of the invention in which an exclusive privilege orproperty is claimed are defined as follows:

1. A gas-filled disconnect contact for metal-clad switchgear comprising,in combination;

a grounded conductive housing;

a bus conductor within said housing and having a terminal end; and astationary contact structure on said terminal end ofsaid bus conductor;

a switchboard bushing of insulation material enclosing said terminal endof said bus conductor; said switchboard bushing comprising a cylinderextending beyond said terminal end of said bus conductor and containingan internal barrier defining a closed pressure chamber filled with gasat a first pressure and surrounding said terminal end of said busconductor and an open-ended chamber extending beyond said barrier;

a first sealing means connected to the outer end of said open-endedchamber for receiving cooperating sealing means to seal said open-endedchamber;

a circuit breaker movable relative to said grounded housing and having acircuit breaker insulation bushing extending therefrom;

said circuit breaker insulation bushing enclosing a circuit breakerconductor which extends beyond the end of said circuit breakerinsulating bushing; and a contact structure on the end of said circuitbreaker conductor;

a second sealing means connected with said circuit breaker bushing forengaging said first sealing means, thereby to seal said open-endedchamber when said circuit breaker is moved to a connected positionrelative to said grounded conductive housing;

and an intermediate sliding contact slidably mounted within saidinternal barrier for slidably engaging said contact on said circuitbreaker conductor when said circuit breaker is moved to its saidconnected position;

operating means for moving said intermediate sliding contact intoengagement with said stationary contact structure of said bus conductorwhile maintaining contact with said circuit breaker conductor;

and means for filling said open-ended chamber with a highdielectric gasafter said circuit breaker is moved to its said connected position andsaid open-ended chamber is sealed, whereby all conductive componentswithin said open-ended chamber are insulated from adjacent portions ofsaid grounded conductive housing by said gas.

2. The device of claim 1 wherein said grounded conductive housingincludes a metallic shutter movable between an 0bscuring and an openposition relative to said open-ended chamber.

3. The device of claim 1 wherein said operating means for moving saidsliding contact includes a piston mounted for 3 ,621 1 7O 5 6 movementwithin said circuit breaker bushing and which is connected to saidsliding contact; and pressure means for conconnected to said slidingcontact; and pressure means for controllably applying pressure to saidpiston for moving said slidtrollably applying pressure to said pistonfor moving said sliding contact. ing contact. 6. The device of claim 5wherein said piston includes a valve movement within said circuitbreaker bushing and which is

1. A gas-filled disconnect contact for metal-clad switchgear comprising,in combination; a grounded conductive housing; a bus conductor withinsaid housing and having a terminal end; and a stationary contactstructure on said terminal end of said bus conductor; a switchboardbushing of insulation material enclosing said terminal end of said busconductor; said switchboard bushing comprising a cylinder extendingbeyond said terminal end of said bus conductor and containing aninternal barrier defining a closed pressure chamber filled with gas at afirst pressure and surrounding said terminal end of said bus conductorand an open-ended chamber extending beyond said barrier; a first sealingmeans connected to the outer end of said openended chamber for receivingcooperating sealing means to seal said open-ended chamber; a circuitbreaker movable relative to said grounded housing and having a circuitbreaker insulation bushing extending therefrom; said circuit breakerinsulation bushing enclosing a circuit breaker conductor which extendsbeyond the end of said circuit breaker insulating bushing; and a contactstructure on the end of said circuit breaker conductor; a second sealingmeans connected with said circuit breaker bushing for engaging saidfirst sealing means, thereby to seal said open-ended chamber when saidcircuit breaker is moved to a connected position relative to saidgrounded conductive housing; and an intermediate sliding contaCtslidably mounted within said internal barrier for slidably engaging saidcontact on said circuit breaker conductor when said circuit breaker ismoved to its said connected position; operating means for moving saidintermediate sliding contact into engagement with said stationarycontact structure of said bus conductor while maintaining contact withsaid circuit breaker conductor; and means for filling said open-endedchamber with a highdielectric gas after said circuit breaker is moved toits said connected position and said open-ended chamber is sealed,whereby all conductive components within said open-ended chamber areinsulated from adjacent portions of said grounded conductive housing bysaid gas.
 2. The device of claim 1 wherein said grounded conductivehousing includes a metallic shutter movable between an obscuring and anopen position relative to said open-ended chamber.
 3. The device ofclaim 1 wherein said operating means for moving said sliding contactincludes a piston mounted for movement within said circuit breakerbushing and which is connected to said sliding contact; and pressuremeans for controllably applying pressure to said piston for moving saidsliding contact.
 4. The device of claim 1 wherein said sliding contactcomprises a conductive plunger having stop means thereon disposed withinsaid closed pressure chamber; said plunger being normally biased awayfrom said stationary contact structure by the gas pressure within saidclosed pressure chamber.
 5. The device of claim 4 wherein said operatingmeans for moving said sliding contact includes a piston mounted formovement within said circuit breaker bushing and which is connected tosaid sliding contact; and pressure means for controllably applyingpressure to said piston for moving said sliding contact.
 6. The deviceof claim 5 wherein said piston includes a valve therein for ventingpressure from the interior of said circuit breaker bushing to the end ofsaid plunger adjacent said piston and means for varying the pressurewithin said circuit breaker bushing between a second and third pressurewhich causes forces on said plunger which are respectively greater thanand less than the opposing force on said plunger due to the gas pressurein said closed pressure chamber.